My sliding sunroof does not work. It seems as if something broke loose that causes it to slide back. The back part will lift up, but with some difficulty. Once its lifted it barely wants to close, sometimes I need to push it down. The crank from the trunk driver side does not allow me to open it either. I can turn the knob, but nothing happens. The motor functions just fine. If I lift the back portion up with the switch and then try to slide the switch back to close the roof, there is a black panel between the outside and interior that I can see slide back and it will sound as it normy would when sliding back and then it appears to stop in the correct location, but the roof itself doesn't move. Any suggestions on how to fix this?

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1990 190E 3.0L